Vertebrate tissues and organs often fail to recover normal form and function when damaged and often fail (due to metabolic and/or mechanical trauma) to adequately integrate with a host when transplanted. In attempts to reconstruct tissues and organs; surgeons have implanted either living tissues or non-living materials in place of damaged or resected native anatomical structures. These traditional techniques have limitations. For example while autografts are histocompatible, the loss of tissue from the donor site often creates anatomical and/or physiological pathologies in the very same host. On the other hand, transplanted allografts and xenografts often provoke a pathological immune response which is proximal to the rejection of these grafts by the host.
Non-living transplant materials are of marginal utility in the repair and transplant of native tissues, tissue constructs, and organs. Specifically, transplanted non-living materials are especially subject to extrusion, infection, and scar tissue formation.
The use of bioengineered tissue as alternatives to transplanted native tissues and non-living materials has also been described. For example, U.S. Pat. No. 5,902,741 to Purchio et al. teaches a method for culturing cartilage tissue in vitro using a framework inoculated with a nutrient medium bearing cartilage cells or precursors. Similarly, U.S. Pat. No. 5,928,945 to Selektar et al. teaches a process for producing bioengineered neo-cartilage by applying fluid-flow shear flow stress to chondrocytes. In another example U.S. Pat. No. 6,080,194 to Pachence et al teaches a template for producing articular cartilage comprising a dense collagen matrix placed on the surface of the cartilage defect to prevent cell migration and vascular in-growth from the sub-chondral plate.
However, these compositions and methods (in the prior art) only approximate a fraction of the anatomical and physiological repertoire of the native tissue they are attempting to replace. More specifically, these shortcomings in the prior art may, in part, be attributed to the inability to uniformly seed, culture, and differentiate cells across the entire cross section of a three-dimensional cellular support layer. What is needed, therefore, are transplantable tissue and tissue constructs that can support cells in their normal metabolic state and can anatomically and physiologically integrate with a host without provoking a pathogenesis.